1. Field of the Invention
The present invention relates to a connection number translating device and its method for translating a connection number represented by VPI number and VCI number obtained from an input ATM cell to a system-inside number in an ATM communication system.
2. Description of the Related Art
It is necessary to translate a connection number represented by VPI (Virtual Path Identifier) number and VCI (Virtual Channel Identifier) number to a system-inside number, for example, when building a system in accordance with a part of all the connections represented by VPI and VCI numbers, in an ATM (A synchronous Transfer Mode) communication system. In some cases, a CAM (Contents Addressable Memory) may be used for this translation. Generally, a CAM may be used to translate the connection number to the system-inside number as well as to recognize address of LAN. This kind of conventional technique is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 6-205025, xe2x80x9cCombination Hash Table and CAM Address Recognitionxe2x80x9d, Japanese Patent Publication Laid-Open (kokai) No. Heisei 6-261078, xe2x80x9cTable Retrieval Method and Routerxe2x80x9d, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 8-70319, xe2x80x9cPacket Processing Method in LAN bridge systemxe2x80x9d.
The Patent Publication No. Heisei 6-205025 discloses a technique of specifying destination at high speed by use of a hierarchical address format enabling direct retrieval of destination and retrieving address database by use of a CAM in an ATM communication system.
The Patent Publication No. Heisei 6-261078 discloses a technique adopted to register a many times-retrieved destination address in a cache memory by providing it with a correspondence table and a CAM as a cache memory for routing table retrieval, constituted in that a plurality of network interfaces within a router respectively comprise a filtering controller and a routing controller, the filtering controller including a filtering table, the routing controller including a CAM for putting a retrieval key, a correspondence table for putting a pointer, and a routing table.
The Patent Publication No. Heisei 8-70319 discloses a technique of taking in a packet on a system bus, filtering a destination address and a source address through a CAM, deciding abandonment or interruption of some object packet based on the filtering result of the destination address, and registering address data into a CAM when judging that it is necessary to learn the address from the filtering result of the source address.
FIGS. 6 and 7 show constitutional examples of a translating device for translating a connection number to a system-inside number in this kind of the conventional technique. The translating device shown in FIG. 6 is a constitutional example in the case where a system operates associated with only the VP connection discriminated by the VPI number. The translation table of a CAM 61 consists of a data field with only the VPI numbers registered, and each address specified by each VPI number is associated with each system-inside number. A CAM access unit 62 performs the setting and retrieval of the CAM 61 as follows. At first, at the setting (RAM mode), only the VPI number is set on a CAM address corresponding to some system-inside number.
At the retrieval (CAM mode), a VPI/VCI acquiring unit 63 acquires the VPI number and the VCI number from the input ATM cell and supplies only the VPI number to the CAM access unit 62, and the CAM access unit 62 retrieves the CAM 61 based on the supplied VPI number. A retrieved address, an unconformity flag, and a plural-conformity flag, that are the results of this retrieval, are sent to a system-inside number judging unit 64 through the CAM access unit 62. The system-inside number judging unit 64 supplies the judgement result including the system-inside number, non-setting alarm, and bad setting alarm according to the retrieval result. When there exists a retrieved address, the retrieved address is supplied as the system-inside number, and when there exist a plurality of retrieved addresses, a plural-conformity flag is generated and the bad setting alarm is supplied. When there exists no retrieved address, an unconformity flag is generated and the non-setting alarm is supplied.
The translating device shown in FIG. 7 is a constitutional example in the case where a system operates associated with the VC connection discriminated by the VPI number and the VCI number. The translation table of a CAM 71 consists of a data field with the combinations of VPI numbers and VCI numbers registered, and the address specified by the data field is associated with the system-inside number. In this case, the CAM 71 is subject to connection setting by the VPI and VCI numbers at the setting (in RAM mode), and it is subject to retrieval by use of the both VPI and VCI numbers obtained from the input ATM cell at the retrieval (in CAM mode).
As mentioned above, in an ATM communication system, it is necessary to translate a connection number represented by the VPI and the VCI numbers to a system-inside number, for example, when building a system corresponding to a part of all the connection represented by the VPI and the VCI numbers. In this translation by use of a CAM, when the connection associated with a system is only the VP connection or only the VC connection, use of a single CAM, with the original connection number as the data and the corresponding system-inside number as the address, makes it easy to inversely look a required system-inside number (retrieved address) up. However, when a system to be realized deals with the VP connection and the VC connection at once, in other words, when there exist a mix of the VP connection and the VC connection, it is necessary to prepare a CAM for the VP connection and a CAM for the VC connection separately, resulting in an increase in hardware and cost.
An object of the present invention is to provide a connection number translating device and its method capable of translating a connection number without increasing the hardware amount, even in an ATM communication system of mixed VP and VC connections.
According to the first aspect of the invention, a connection number translating device for use in an ATM communication system for translating a connection number specified by VPI number and VCI number of an input ATM cell to a system-inside number, comprises
acquiring means for acquiring the VPI number and the VCI number from the input ATM cell,
a translation table storing combinations of information including VPI and VCI numbers and type information indicating the type of connection decided according to the VPI and VCI numbers as well as system-inside numbers associated with the respective combinations of information,
retrieval means for retrieving the translation table based on the type information and the VPI and VCI numbers acquired by the acquiring means, and
judging means for estimating the retrieval result by the retrieval means so to supply a desired system-inside number,
wherein the retrieval means performing retrieval two times in a first retrieving method of retrieving the translation table, with the VCI number masked, based on the VPI number and the type information indicating a VP connection and in a second retrieving method of retrieving the translation table based on the VPI and VCI numbers and the type information indicating a VC connection,
the judging means deciding a desired system-inside number based on the both retrieval results of the first and second retrieving methods.
In the preferred construction, the translation table registers the VPI and VCI numbers and the type information as the data and it is constituted by a Contents Addressable Memory having a data field including each system-inside number corresponding to each data as address.
In the preferred construction, the judging means judges the corresponding address as a system-inside number corresponding to the VP connection when the first retrieving method detects a corresponding address and the second retrieving method detects no corresponding address, and judges the corresponding address as a system-inside number corresponding to the VC connection when the first retrieving method detects no corresponding address and the second retrieving method detects a corresponding address.
In another preferred construction, the judging means judges the corresponding address as a system-inside number corresponding to the VP connection when the first retrieving method detects a corresponding address and the second retrieving method detects no corresponding address, judges the corresponding address as a system-inside number corresponding to the VC connection when the first retrieving method detects no corresponding address and the second retrieving method detects a corresponding address, judges that any system-inside number corresponding to a connection to be retrieved has not been set up in the translation table when the first and the second retrieving methods detect no corresponding address, and judges that a system-inside number corresponding to a connection to be retrieved has not been properly set up in the translation table, when either the first or the second retrieving method detects a corresponding address of plural-conformity and when both the first and second retrieving methods detect each corresponding address, thereby to supply a desired system-inside number or a message indicating the setting condition of the translation table, depending on the retrieval result of the retrieval means.
According to the second aspect of the invention, a connection number translating method for use in an ATM communication system for translating a connection number specified by VPI number and VCI number of an input ATM cell to a system-inside number, the method comprising the steps of
a step of acquiring the VPI number and the VCI number from the input ATM cell,
a step of storing combinations of information including VPI and VCI numbers and type information indicating the type of connection decided according to the VPI and VCI numbers as well as system-inside numbers associated with the respective combinations of information,
a step of retrieving the translation table based on the type information and the VPI and VCI numbers acquired by the acquiring step, and
a step of estimating the retrieval result by the retrieving step so to supply a desired system-inside number,
the retrieving step includes, at least, a first retrieving step of retrieving the translation table, with the VCI number masked, based on the VPI number and the type information indicating a VP connection, and a second retrieving step of retrieving the translation table based on the VPI and VCI numbers and the type information indicating a VC connection,
the judging step deciding a desired system-inside number based on the both retrieval results of the first and second retrieving steps.
In the preferred construction, in the judging step, when the first retrieving method detects a corresponding address and the second retrieving method detects no corresponding address, the corresponding address is judged as a system-inside number corresponding to the VP connection, and when the first retrieving method detects no corresponding address and the second retrieving method detects a corresponding address, the corresponding address is judged as a system-inside number corresponding to the VC connection.
In the preferred construction, the judging step further includes a step of examining the justness of the detected corresponding address and the setting condition of the translation table, depending on the retrieval result of the retrieving step, and a step of supplying a desired system-inside number or a message indicating the setting condition of the translation table, depending on the examination result, and
in the examination step, when the first retrieving method detects a corresponding address and the second retrieving method detects no corresponding address, the corresponding address is judged as a system-inside number corresponding to the VP connection, when the first retrieving method detects no corresponding address and the second retrieving method detects a corresponding address, the corresponding address is judged as a system-inside number corresponding to the VC connection, when the first and the second retrieving methods detect no corresponding address, it is judged that any system-inside number corresponding to a connection to be retrieved has not been set up in the translation table, and when either the first or the second retrieving method detects a corresponding address of plural-conformity and when both the first and second retrieving methods detect each corresponding address, it is judged that a system-inside number corresponding to a connection to be retrieved has not been properly set up in the translation table.
According to the third aspect of the invention, a computer readable memory storing a control program for controlling a connection number translating device for use in an ATM communication system for translating a connection number specified by VPI number and VCI number of an input ATM cell to a system-inside number, the control program comprises
a step of acquiring the VPI number and the VCI number from the input ATM cell,
a step of storing combinations of information including VPI and VCI numbers and type information indicating the type of connection decided according to the VPI and VCI numbers as well as system-inside numbers associated with the respective combinations of information,
a step of retrieving the translation table based on the type information and the VPI and VCI numbers acquired by the acquiring step, and
a step of estimating the retrieval result by the retrieving step so to supply a desired system-inside number,
the retrieving step includes, at least, a first retrieving step of retrieving the translation table, with the VCI number masked, based on the VPI number and the type information indicating a VP connection, and a second retrieving step of retrieving the translation table based on the VPI and VCI numbers and the type information indicating a VC connection,
the judging step deciding a desired system-inside number based on the both retrieval results of the first and second retrieving steps.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.